clippy: fix clippy::unnecessary_debug_formatting and clippy::io_other_error, adjusting cp tests to align with GNU

[Qelxiros]

On my machine cp a returns the error message cp: missing destination file operand after 'a'. Prior to this PR, uutils double quoted the a. This PR uses Path::display instead of Debug output and quotes the file path with os_display. I also fixed an io::Error-related clippy warning in ln.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

[cakebaker]

Can you please split this PR into two PRs: one for fixing the clippy errors introduced with Rust 1.87 and one for adjusting the cp tests to align with GNU? Thanks!

[cakebaker]

Please ignore my previous comment, I was wrong about this PR. I should have looked at the actual changes, not just the title :|

[Qelxiros]

So the MSRV check here is failing because Path::display didn't get stabilized until 1.87.0, but the clippy checks in e.g. #7940 are failing because they use the latest rust version and deny warnings. @sylvestre do you have thoughts on how to fix this? Has it happened before? Could we change the clippy checks to use MSRV instead of latest? We'd get new checks more slowly, but we wouldn't end up with mutually exclusive checks like we have here.

Side note: I don't think I understand the clippy command. clippy::unnecessary_debug_formatting is in pedantic and allowed by default, and I didn't see anything in the workflow file that looked like it would enable it. So maybe there's another solution (at least for this case) involving the specific arguments we pass to clippy.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

[cakebaker]

An alternative is to change the level for pedantic from warn to allow in Cargo.toml.

[Qelxiros]

I thought about that, but according to #6720 (review), there are several pedantic lints that we (or at least @tertsdiepraam) would want to enforce across the board. (I checked, and the only one that fails on main is uninlined_format_args in one case.)

Looking at the top-level Cargo.toml, it looks like we might be able to add unnecessary_debug_formatting = "allow" to [workspace.lints.clippy] until MSRV is 1.87.0.

[tertsdiepraam]

Just to be clear, in that issue, I would accept the changes suggested by the lint, not necessarily the enforcing of the lint.

[cakebaker]

Closing this PR, some of its changes have been included in #7957. Thanks!